1. Field of the Invention
The present invention relates to a transmission structure for an automotive vehicle, and, more particularly, to a transmission structure which prevents a power unit formed by an engine and a transmission, from shaking or vibrating.
2. Description of the Prior Art
Conventionally, it is well known to provide a front wheel drive vehicle or a four wheel drive vehicle with an engine having its crankshaft located in a transverse direction of the vehicle body. Such a vehicle has a power unit formed by an engine and a transmission case around the crankshaft. The transmission case is normally structured so as to include a clutch case, which accommodates a clutch and a gear case which accommodates a transmission gear assembly. A differential case, which accommodates differential gears, can be assembled integrally or separately with the clutch case. The differential case is typically disposed in front of the clutch case and parallel to the crankshaft of the engine. The transmission case is generally composed of a plurality of functional units.
In order to reduce shaking or vibration generated in the power unit, several technical innovations have been made. For example, Japanese Laid open Utility Model Application No. 61-70543 shows a reinforcing structure in which a corner portion, made in assembling the engine reinforces the transmission. According to this structure, although the engine and the transmission case can be firmly connected, shaking or vibration is not reduced by the reinforcing structure, since the transmission case is composed of a plurality of functional parts.
It has been found that an engine disposed in a transverse direction of the vehicle, with a differential case disposed in front of the engine and parallel to the crankshaft,
is subject to severe shaking or vibration in a transmission case, since the transmission case itself generates some vibrations such as bending vibration and torsional vibration. In particular, due to low stiffness, when the transmission case is divided into a plurality of parts, shaking or vibration will become worse.
On the other hand, a transmission case is structurally complex, and it is necessary to include on the transmission case some mounting elements so as to mount the case on a vehicle body. Also, the transmission case is required to be more compact to save space in a narrow engine compartment. Such makes it difficult to increase stiffness by adding new parts in the transmission case. Accordingly, it is strongly desired to establish a reinforced structure which is usable in a limited space by using smaller size reinforcement elements.